My U.S. Pat. No. 7,207,281 deals with quilting machines, more particularly with a drive arrangement for computerized hand-guided quilting device. The basic properties of quilting machines and the way how they can be moved over a fabric to be quilted can be learned.
Further conventional quilting machines are available in the market supplied by Gammill Inc. West Plains (Mo.) having the commercial names of Premier and the Vision Series, and their detailed structures can be found and downloaded from the website of the company: www.gammill.com. The basic design of these prior art quilting machines is described in connection with FIG. 1 at a later part of the present specification, wherein the FIG. 1 also shows the size of a conventional domestic or industrial sewing machine. From FIG. 1 it is clearly visible that the upper surface of the free end portion of the lower arms of the quilting and sewing machine is a planar surface and it defines the bottom of a throat gap, which is just large enough to accommodate the stroke range of the needle. The passage size of the quilting machine is much deeper and higher, therefore the needle structure is arranged in a downwardly projecting front end portion of the upper arm, and a separate needle path extension or guide is provided. Here the needle performs a special alternating movement in the vertical plane, and the movement is transformed from the rotation of an upper drive axle extending along the upper arm of the machine housing, called also as C-frame. The need for the vertical extension has increased the mass of the vertically moving elements, and with higher mass, the driving axle is exposed to higher loads and to the vibration effect of such reciprocal movement. While the C-frame of the quilting machine is substantially larger and heavier compared to that of the conventional sewing machines, the accuracy requirements on the needle-bobbin alignment are the same. In case of larger distances and masses, it is rather difficult to ensure the same degree of precision. These problems have been solved by using a highly reinforced and massive C-frame with high weight and size, and the upper and lower axles extending along the full arm lengths have been made by massive solid shafts of also extended size. With such dimensions, any imbalance in the rotating masses can cause misalignment, and the load acting on the arms of the C-frame tend to excite vibration which also contributes to misalignment.